Sawtooth wave generator



Spt. 23, 19.52 R, K LOCKHART 2,611,872

SAWTOOTH WAVE GENERATOR Filed March 5l, 1949 INVENTOR 1mg-Humm;

TTORNEY Patented Sept. 23, 1952 oNrn:'o gsnvrcs PATENT ortica Robert K1 Lockhart. Collingswood, Aj., assignor to Radio Corporation of America, a corporation of Delaware npiiueanoaMarch si, 1s4asria1n. 84,526

4 claims. (ci. 25o- 36) y 'I'he present invention producing non-sinusoidal waves and more particularly, but not necessarily exclusively. to such generatorsfor lproducing linear sawtooth waves.

In accordance with thepresent invention novel means are provided for obtaining compensation `for the wave form of the output of a -sawtooth wave generator so` that a linear deflection of a 'cathode Vray beam, for example, can be produced.

The principal aim lor object of 'the present invention is to provide novel means for compensa'- tion in theproduction o i a sawtooth wave form whereby a linearsawtooth is obtained'. Y

Another object is to provide a novel wave form compensation means for blocking oscillator.

A further object is Vto provide a blocking oscillator with a cathode compensation circuit including a condenser which char-ges during retrace time and discharges during the forward trace time to add its voltage wave form algebraically to the voltage appearing on the plate of the blocking oscillator to produce a linear sawtooth wave.

Otherv objects `and advantages of the present invention will, of course, rbecome 4apparent. and. immediately `suggest themselves to those .skilled in the art to which the invention is `directed from a Aread-ingof the following specification in connection fwith the accompanying drawings in which? Fig. yl is a diagrammatic illustration of a sawtooth generator embodyingthe invention. and

Fig. V2 shows conventionally the output wave form of the .generator of .1 when operating in faccordance with the invention.

Referringto Fig. 1 oi thejdrawings, there is shown byway of example a blocking oscillator Vil) comprising an oscillator tube t2. The electrode circuitsof the tube t2 are connected substantially as shown in Tclson-Reissue Patent Re. 20,338 `so that it can function as :a blocking oscillatonf A Ablocking oscillator .is 'also shown and described -by Tclson et `al. in U. S.` Patent No.` 2,101,520, granted :December 7, 1937. A transformer I4, preferably having an iron core as indicated on the drawing, provides an inductive coupling between the grid and .plate circuits. A blocking condenser IB is connected, vas showrnbetween the grid I8 of the tube '[2 and the grid winding 2| of the transformer I4. A resistance 22 which may be adjustable, if desired, provides la leakagepath to ground forvthe electrical charge stored 4in the condenser I6. Theiplate `'circuit of the ltube V|-2-includes the primari1 l2li of the transformer 4I d `and terminates at the positive f-terminal of a D.C. voltage supply=fsource (not shown) relates to generators `for Y 2. I as indicated schematically at 25. The plate circuit of the tube I2 also includes a 'resistor 21.

The functioning of the tube l2 with a `circuit arrangement shown is such as to produce current pulses which cause a sawtooth voltage wave to appear across a condenser 28. 'Ihe previously mentioned resistor `2"! ycontrols the charging cycle of the condenser 2B. The sawtooth voltage Wave across the condenser is indicated `conventionally at 3| and is substantially linear in accordance with the invention as will `be pointed out in connection with Fig. 2 lof the drawing. The voltage wave 3l is of a shape which will be effective to cause deiiection in the cathode ray beam in any well-known manner, for example, v

as shown in the Tclson reissue patent mentioned above. Since the sawtooth voltage wave 3| is substantially linear, the oscillator of Fig. 1 `of the drawings embodying theinvention `is particularly suited for. use with a control deflection arrangement of l'the `type shown in U. S. Patent No. 2,587,313 issued to G. VL. Grundmann on February 26, .1952, `for Automatic Control of Wave Form. p t

In general, with a blocking oscillator,I not including the improvement of the present invention, the condenser 2B is charged fromthepositive potential applied to the terminal 26 through resistor 21 and resistor 33 `with point 18 grounded. This charging curve 36 can be no vmore linear than a small portion of the exponential charge curve of a condenser. When the tube l2 becomes conductive during one part of the well-known .blocking oscillator cycles, the condenser 28 is discharged more or less abruptly. The charging curve for the condenser 28 is represented by the line 36 of the wave form '3| as shown in Fig. 2 of the drawings. While the vconventionally shown wave form 3l, as shown in Figs. 1 and 2 does not take into account `the presence ofthe resistor l33, it may serve to provide high-peaking where the form of `voltage 31 is to `be of the shape required to cause a sawtoot-h ycurrent wave `to pass through an inductive circuit having resistance, for example, the 'circuit 'represented `by 'the '.primary winding-cia deflectiontransiormer.

In accordance with the invention, 'the exponentia-l curvature 30 "is corrected by the 'addition of anaddit'ional -sawto'othfwhose curvature is #equal and opposite to that -of the exponential curve 36." This is *accomplished -in 1accordance withthe present invent-ion by L'aparallel resistor condenser combination havinga selected time constant. This parallel combination is added, as shown, inl the cathode circuit df the discharge tubefandicomprises the previously 'mentioned re# aeiira sistor 34 and a condenser 38. The condenser 38 v charges during the retrace time 4| of the Wave Y 3l and discharges during the forward trace time 38 to add its voltage wave form algebraically to that of the plate of the tube I 2 to provide linearity of Wave form `4shown illustratively as the wave 3l in Figs. 1 `a'nd--Z'of the drawings. Atthe beginningoi each cycle of the wave 3l represented by the initiation of the charging of the con-` denser 28 the voltage across the condenser 38 is at its maximum value, thus reducing the effective charging voltage at the point 26 toward which the condenser V28Y starts to charge, Asl the charge on theYV condenser 28 increases, the charge on the condenser 38 decreases so that the eiective charge voltage increases.

It will thus be seen that the inherently known linear charging curve T=period` of the charging time of condenser 28 (time duration of curve 36).. i What is claimed isz` 1. An oscillator for producing a voltage of VsaWtooth Waveform comprising a vacuum tube having a cathode, a control electrode, and-an anode, an anode circuit connected to said anode, a control electrode ,circuit connected tor said' control electrode, means for ycoupling f said control electrode circuit and said lanode circuit, a source of positive potential for said anode circuit, a resistor in saidv anode circuit, one terminal vof said resistor being connected to said source of positive potential, a condenser having one terminal thereof connected toy the terminal of said resistor opposite the terminal connected to said sourceof positive potential, means connecting the other terminal of said condenser directly to saidcathode, said condenser being'periodically discharged upon establishingow of current in saidv anode circuit, la time constant combination comprising a resistance and ka condenser in parallel, one terminal of said combination being connected to Ysaid'` cathode, the otherl terminal of said combination being connected to a voltage reference point. in said circuit, saidv time constant combination having a time constant 'ofwpositive' potential for said anode circuit, a resistor in lsaidanode circuit, i, one terminal of said resistor beingjlconnected to said;source of positivey potential, a condenser having one terminal thereof connected vto the terminal of said resistor opposite the terminal connected to said `.source of positive potential,- asecond resistor. they other terminal of saidcondenser being connected Vthroughsaid second resistor directly to n said cathode, said condenser being periodically discharged upon establishing flow of current iii said anode circuit, a time constant combination comprising a resistance and a condenser in parallel, one terminal of said combination being connected to said cathode, the other terminal of said combination being connectedto a voltage reference point insaid circuit, said time constant combination having a time constant where T is equal to the time of the sawtooth Wave represented bygthe charging time of Vsaid first named condenser.;

3. An oscillator forproducing a voltage of sawtooth waveform comprising a vacuum tube having a cathode, a control electrode, and an anode, an anode circuit connected to said anode, a control electrode circuit connected to said control electrode, means'lfo'r coupling said control electrode circuit and said anode circuit, a source of positive potential for said anode "circuit, a resistor in said anode circuit, one terminal of said resistor being connected to said source' of positivepotential, a condenser having onefterminal thereof connected to the terminal of said resistor opposite the terminal connected to said source of positive potential, a second resistor, the other terminal of saidcondenser being connected through said second resistor directlyto said cathode, said condenser being periodically discharged upon estabv lishing flow of current in said anode circuitja e time constant combination comprising -a resistance and a condenser is parallel, one terminal of said i combination being connected to cathode, lthe other terminal of saidcombination being connected to a voltage reference point in said circuit. y

4. An oscillator` for producing a Voltage of sawtooth waveform comprising ayacuum tube having a cathode, a control electrode, and an anode, an anode circuit connected to said anode,

a` control electrode circuit connected to said control electrode, a transformer coupling said control electrode circuit and said anode circuit, a source ofvpositive potential for said anode circuit, a resistor in said anode circuit, one terminal of said resistor being connected to said source of positive potential, a condenser having one terminal'thereofv connected to the terminal of said resistor opposite the terminal connected to said sourceof Vpositive potential, a second resistor, Vthe `other terminal of said condenser being connected throughvlsaid second resistor directly to'said cathode, said condenserA being periodically discharged upon establishing flow of current in said anode circuit, a time`v constant combination comprising a resistance and ay angenehmes CITED' i The ollowing 'references are of record in the iile ofv this patent:

i UNITED STATES PATENTS Number said 

